CHA zeolite is zeolite having a CHA framework defined by the International Zeolite Association (IZA). In general, CHA zeolite is synthesized by a method using an organic structure directing agent (hereinafter referred to also as SDA) as in PATENT DOCUMENT 1. It is also possible to synthesize CHA zeolite by a method using no SDA as in PATENT DOCUMENT 2.
CHA zeolite can be used, for instance, for separating gases, reducing nitrogen oxides contained in automobile exhaust gas, and converting lower alcohols and other oxygen-containing hydrocarbons into liquid fuel, and as a catalyst for producing dimethylamine. These applications utilize pores derived from a zeolite framework of CHA zeolite and CHA zeolite having high crystallinity is therefore required.
CHA zeolite also has a problem in that its zeolite framework is broken when the CHA zeolite is exposed to high temperatures in the presence of moisture (hydrothermal resistance). For instance, when CHA zeolite having low hydrothermal resistance is used to reduce nitrogen oxides contained in automobile exhaust gas or to remove hazardous components in gas emissions from factories, its zeolite framework is broken during use and its inherent performance cannot be therefore exhibited.